In general, a plastic flat display is applied to an LCD (Liquid Crystal Display), an organic EL (Electro Luminescent) display, an electronic ink and the like.
FIG. 1 is a sequential process view illustrating a conventional plastic liquid crystal display and a method for manufacturing the same.
The method for manufacturing the conventional plastic liquid crystal display as illustrated in FIG. 1 will be described below.
1. Upper and lower transparent ITO (Indium Tin Oxide) film layers are bonded to base films, respectively.
2. The upper and lower ITO film substrates are patterned (photolithography process).
3. An alignment layer is coated on each of the upper and lower ITO film electrode substrates.
4. A thermosetting sealant is printed on one substrate (the upper substrate).
5. Spacers are distributed on the other substrate (the lower substrate).
6a. The one substrate (the upper substrate) and the other substrate (the lower substrate) are aligned with and assembled to each other through thermal pressing.
6b. Liquid crystals are injected under a vacuum condition into a space between the one substrate (the upper substrate) and the other substrate (the lower substrate).
FIG. 2 is a sequential process view illustrating a conventional flexible printed circuit board (FPCB) and a method for manufacturing the same.
The method for manufacturing the conventional flexible printed circuit board as illustrated in FIG. 2 will be described below.
1. A base film made of a material such as polyimide is prepared.
2. A thin copper layer is plated on the base film.
3. The plated copper layer is etched through a photolithography technique to form an electrode pattern.
4a. A protection film is bonded through thermal pressing. Here, 4b of FIG. 2 is a perspective view of 4a. 
5a. To prevent a copper surface exposed in a region without the protection film from being oxidized, surface treatment such as electroless gold plating or electroless silver plating is performed to form a protection film. Here, 5b of FIG. 2 is a perspective view of 5a. 
FIG. 3 is a sectional view illustrating a bonding process of the conventional plastic liquid crystal display and flexible printed circuit board.
The bonding process illustrated in FIG. 3 will be described below.
1. An electroconductive material, such as solder or an anisotropic conductive film (ACF), is bonded on a pad electrode portion of a plastic LCD to be bonded to a FPCB.
2. The FPCB and the plastic LCD are aligned with each other and thermally pressed to each other.
FIG. 4 is a side view showing the structure of a conventional reflective LCD, and
FIG. 5 is a plan view showing the structure of the conventional reflective LCD of FIG. 4.
The structure and principle of the conventional reflective LCD will be described as follows:
1. Structure
The conventional reflective LCD comprises an upper ITO electrode substrate with a polarizer attached thereto and a lower ITO electrode substrate with an inner reflection layer (or an external reflection film). The conventional reflective LCD has a structure in which the two substrates are bonded to face each other, and liquid crystals are interposed between the upper and lower ITO electrode substrates.
2. Principle
An ITO pad portion of an ITO electrode, which is exposed out of an LCD cell, and an electrode portion of a FPCB (Flexible Printed Circuit Board) are bonded to be electrically conducted to each other. Accordingly, an external electrical signal is transmitted to the upper and lower substrates of an LCD through the FPCB, and liquid crystals are reacted in accordance with a change in an electric field between the upper and lower substrates, which is generated by the external electrical signal, so that the amount of light emitted while being reflected on a reflection plate can be adjusted.
However, such a conventional reflective LCD has problems as follows:
First, since costs of the upper and lower ITO electrode substrates have a very high fraction in costs of the LCD, there is a problem in that manufacturing costs increase due to the upper and lower substrates.
Further, there are other problems in that a percentage defective increases and manufacturing costs also increase due to the complicated processes in which an LCD cell is manufactured using the upper and lower ITO electrode substrates and the FPCB is then bonded to the ITO pad electrode by aligning them with each other.
FIG. 6 is a side view showing the structure of a conventional transmissive LCD, and
FIG. 7 is a plan view showing the structure of the conventional transmissive LCD of FIG. 6.
The structure and principle of the conventional transmissive LCD will be described as follows:
1. Structure
The conventional transmissive LCD comprises upper and lower ITO electrode substrates each of which has a polarizer attached thereto. The conventional transmissive LCD has a structure in which the two substrates are bonded to face each other and liquid crystals are interposed between the upper and lower ITO electrode substrates
A BLU (Back Light Unit) serving as a light source is positioned below the lower
ITO electrode substrate.
2. Principle
An ITO pad portion of an ITO electrode, which is exposed out of an LCD cell, and an electrode portion of a FPCB are bonded to be electrically conducted to each other. Accordingly, an external electrical signal is transmitted to the upper and lower substrates of an LCD, and liquid crystals are reacted in accordance with a change in an electric field between the upper and lower substrates, which is formed by the external electrical signal, so that the amount of light emitted from the BLU can be adjusted.
However, such a conventional transmissive LCD has problems as follows:
First, since costs of the upper and lower ITO electrode substrates have a very high fraction in costs of the LCD, there is a problem in that manufacturing costs increase.
Further, there are other problems in that a percentage defective increases and manufacturing costs also increase due to the complicated processes in which an LCD cell is manufactured using the upper and lower ITO electrode substrates and the FPCB is then bonded to the ITO pad by aligning them with each other.
FIG. 8 is a sectional view conceptually showing a conventional organic EL display.
The structure and principle of the conventional organic EL display will be described as follows:
1. Structure
A single-layer EL device has a structure of electrode/emitting material layer/electrode. Ca, Mg, Al or the like, which has a small work function, is used for a cathode that is an electron injection electrode.
An anode is a hole injection electrode. A transparent metal oxide with a high work function is used for the anode so that emitted light can be radiated out of the device. ITO (Indium Tin Oxide) is most widely used for the hole injection electrode, and the thickness of the ITO is about 30 nm.
Glass is generally used for a substrate. The material of the emitting material layer (EML) includes a single molecule organic EL such as Alq3 or Anthracene, PPV (poly(p-phenylenevinylene)), PT (polythiophene) and the like, and polymeric organic EL materials that are derivatives thereof.
Further, an FPCB is positioned on a top surface of an electron emitting layer.
2. Principle
When power is supplied to the organic EL display, a current flows while electrons are moved. In a cathode, electrons are moved to the emitting material layer by an assistance of an electron transmission layer, whereas in an anode, holes (the concept of positive(+) and a state where electrons escape) are moved to the emitting material layer by an assistance of a hole transmission layer. Further, electrons and holes, which are combined in the emitting material layer made of an organic material, produce excitons with high energy. At this time, light is emitted while the excitons hop to a lower energy level.
However, such a conventional organic EL display has a problem as follows:
First, there are problems in that a percentage defective increases and manufacturing costs also increase due to the complicated processes in which a single-layer EL device is manufactured and an FPCB is bonded thereto.